During surgical implantation of femoral condylar prostheses, it is typically necessary to utilize some type of tool to gauge whether or not the distal aspect of the femur has been properly sized to receive the condylar implant. This gauge typically resembles the actual prosthesis which will be implanted. The surgeon first "resects" the surface of the bone to match the geometry of the implant by making several cuts as shown, for example, in U.S. Pat. No. 4,474,177 to Whiteside, the entire disclosure of which is expressly incorporated by reference herein and relied upon.
Once the distal aspect of the femur has been resected, a convex patellar groove is formed in the anterior surface of the resected bone, in order to accommodate the mating concave patellar track of the condylar implant. The external distal surface of the condylar implant, particularly that of the patellar track, articulates with the proximal aspect of the tibia, which is also resected to receive a tibial implant in a total knee replacement. The present inventors have previously devised a cutting guide for shaping the patellar groove in allowed U.S. patent application Ser. No. 462,268, filed Jan. 9, 1990, the entire disclosure of which is expressly incorporated by reference herein and relied upon. Depending upon the degree of knee reconstruction indicated, a patellar prosthesis may also be implanted as shown, for example, in U.S. patent application Ser. No. 466,093, filed Jan. 12, 1990 in the name of the instant inventors, the entire disclosure of which is expressly incorporated by reference herein and relied upon.
A challenge confronted by condylar implant systems is the need to both accurately form a patellar groove in the resected surface of the distal femur and perform a trial reduction of the knee joint to ascertain proper sizing of the condylar implant. This is conventionally a sequential procedure employing first a guide seated on the resected bone for engaging a shaping tool which forms the patellar groove in the bone. Secondly, a trial condylar implant is seated on the resected surface of the distal femur, having a size and shape resembling that of the permanent condylar prosthesis actually being implanted, after which the trial reduction of the knee is performed by articulating the femur and tibia. Following satisfactory trial reduction, the trial implant is removed and replaced by the permanent condylar implant. A disadvantage of the procedure set forth above is degradation of the bone caused by alternate insertion and removal of separate track cutting and trial implant guides, respectively. Moreover, use of separate track cutting and trial implant guides is relatively inefficient and time-consuming, further complicating the surgical procedure for reconstructing the knee joint.
Accordingly, there is a need for a device and method which combine the features of a femoral trial implant and patellar track cutting guide, so that the patellar groove may be shaped and a surgical trial reduction accurately performed using the same instrumentation.